A slash pairing from the anime Naruto involving the brothers Itachi and Sasuke Uchiha. Itachi is six years older than Sasuke, and Sasuke has lived his life for the sole purpose of killing Itachi for revenge after he slaughtered their clan.
ItaSasu refers to Itachi as the seme; the dominant one; the one 'on top' and Sasuke as uke; the submissive one; the partner 'on the bottom'.

Itachi's a mass murderer and Sasuke's a coldhearted emo, but they're perfect for each other since nobody else understands them; ItaSasu is just so beautiful!